Heat storage tank in cooling water circuit

ABSTRACT

In a heat storage tank, first and second valve bodies are disposed to open and close first and second valve ports, respectively. A density of the first valve body is made larger than that of cooling water, and a density of the second valve body is made smaller than that of cooling water. When the dynamical pressure due to cooling water is applied to the first and second valve bodies, the first and second valve ports are opened by the first and second valve bodies. On the other hand, when the dynamical pressure is not applied to the first and second valve bodies, the first valve body closes the first valve port by the weight of the first valve body, and the second valve body closes the second valve port by the buoyancy.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application is related to Japanese Patent Applications No.2000-310869 filed on Oct. 11, 2000, and No. 2001-226223 filed on Jul.26, 2001, the contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a heat storage tank which storesa cooling liquid of a liquid-cooled engine such as a water-cooled engineby heat insulation. For example, the heat storage tank is suitably usedfor a vehicle having a water-cooled engine.

[0004] 2. Description of Related Art

[0005] In a conventional heat storage tank described in JP-A-10-77839, aflow of cooling water is controlled by an electrical valve. Because theelectrical valve is used for controlling the flow of cooling water inthe heat storage tank, component number is increased, a structure of theheat storage tank becomes complex, and a production cost of the heatstorage tank is increased.

SUMMARY OF THE INVENTION

[0006] In view of the foregoing problems, it is an object of the presentinvention to provide a heat storage tank which is manufactured in lowcost.

[0007] According to the present invention, in a heat storage tank forstoring a cooling liquid of a liquid-cooled engine in a cooling liquidcircuit by heat insulation, a fluid passage communicating with aninterior of a tank body is provided, and a valve body for opening andclosing the fluid passage is constructed to open the fluid passage whena dynamical pressure due to the cooling liquid, larger than apredetermined pressure, is applied to the valve body, and to close thefluid passage when the dynamical pressure smaller than the predeterminedpressure is applied to the valve body. Accordingly, the flow passage canbe accurately opened and closed without using an electrical valve.Therefore, the heat-storage tank can be manufactured in low cost.

[0008] Preferably, the valve body is constructed to close the fluidpassage by a density difference between the cooling liquid and the valvebody when the dynamical pressure applied to the valve body is smallerthan the predetermined pressure. Alternatively, the valve body isconstructed to close the fluid passage by a pressure due to a weight ofthe valve body and a weight of the cooling liquid when the dynamicalpressure applied to the valve body is smaller than the predeterminedpressure. Therefore, the structure of the valve body can be made simplein the heat storage tank.

[0009] The cooling liquid circuit includes a first liquid circuit havingat least a radiator for cooling the cooling liquid, and a second liquidcircuit including the heat storage tank. A pump is disposed in thesecond liquid circuit so that cooling liquid circulates between thesecond liquid circuit and the liquid-cooled engine independently withthe first liquid circuit. Therefore, high-temperature cooling liquidstored in the heat storage tank can be directly supplied to the enginewithout being affected by operation of the first liquid circuit. Thus,heating operation of the engine can be effectively facilitated.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Additional objects and advantages of the present invention willbe more readily apparent from the following detailed description ofpreferred embodiments when taken together with the accompanyingdrawings, in which:

[0011]FIG. 1 is a schematic diagram showing a cooling water circuitaccording to a first preferred embodiment of the present invention;

[0012]FIG. 2 is a schematic diagram of a heat storage tank according tothe first embodiment;

[0013]FIG. 3 is a front view of a plate member used for restricting amixing of cooling water in the heat storage tank according to the firstembodiment;

[0014]FIG. 4 is a schematic diagram showing a flow of cooling water inthe heat storage tank of the first embodiment;

[0015]FIG. 5 is a schematic diagram showing a heat storage tankaccording to a comparison example of a second preferred embodiment ofthe present invention;

[0016]FIG. 6 is a schematic diagram showing a heat storage tankaccording to the second embodiment;

[0017]FIG. 7 is a schematic diagram showing a heat storage tankaccording to a third preferred embodiment of the present invention;

[0018]FIG. 8 is a schematic diagram showing a flow of cooling water inthe heat storage tank according to the third embodiment;

[0019]FIG. 9 is a schematic diagram showing a heat storage tankaccording to a fourth preferred embodiment of the present invention; and

[0020]FIGS. 10A and 10B are schematic enlarged diagrams each showing asecond pipe member for a heat storage tank according to a fifthpreferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

[0021] Preferred embodiments of the present invention will be describedhereinafter with reference to the accompanying drawings.

[0022] A first preferred embodiment of the present invention will be nowdescribed with reference to FIGS. 1-4. In the first embodiment, a heatstorage tank 100 of the present invention is typically used for acooling water circuit of a water-cooled engine 200 for a vehicle.

[0023] The water-cooled engine 200 is disposed in the cooling watercircuit to be cooled by cooling water flowing through the engine 200, aradiator 210 is disposed to cool the cooling water by performing a heatexchange between cooling water and air. A bypass passage 220 throughwhich cooling water bypasses the radiator 210 is provided, and athermo-control valve 221 (thermostat) is disposed to adjust a flowamount of cooling water flowing through the bypass passage 220 and aflow amount of cooling water flowing through the radiator 210. Thethermo-control valve 221 (thermostat) adjusts a ratio between the flowamount of cooling water flowing through the bypass passage 220 and theflow amount of cooling water flowing through the radiator 210, so thatthe temperature of the engine 200 can be controlled to a predeterminedtemperature.

[0024] A blower 211 is disposed to blow cooling air (outside air) towardthe radiator 210. A heater core 230 is disposed to heat air blown into apassenger compartment using cooling water in the cooling water circuitas a heating source, and a blower 231 for blowing air to the heater core230 is disposed.

[0025] In the first embodiment, the cooling water circuit includes afirst cooling water circuit S1 through which cooling water in the engine200 circulates the radiator 210, the bypass circuit 220 and the heatercore 230, and a second cooling water circuit S2 through which coolingwater circulates between the heat storage tank 100 and the engine 200. Afirst pump 201 driven by power from the engine 200 is disposed in thefirst cooling water circuit S1 to circulate cooling water in the firstcooling water circuit S1, and a second pump 240 driven electrically isdisposed in the second cooling water circuit S2 to circulate coolingwater in the second cooling water circuit S2.

[0026] The second cooling water circuit S2 is constructed, so thatcooling water flowing from the engine 200 flows into the heat storagetank 100 and cooling water flowing from the heat storage tank 100 flowsinto the engine 200. Because cooling water independently circulates inthe second cooling water circuit S2 by the second pump 240, a flow ofcooling water in the second cooling water circuit S2 can beindependently controlled without being affected by a flow of coolingwater in the first cooling water circuit S1.

[0027] A first temperature sensor 251 for detecting temperature (i.e.,temperature of cooling water circulating in the engine 200) of theengine 200 is disposed in the engine 200, and a second temperaturesensor 252 for detecting temperature of cooling water (hot water)flowing out from the heat storage tank 100 is disposed. Detectionsignals from both the temperature sensors 251, 252 are input into anelectronic control unit (ECU) 250, and the ECU 250 controls theoperation of the second pump 240 based on the detection signals of boththe temperature sensors 251, 252.

[0028] Next, the heat storage tank 100 will be now described in detailwith reference FIG. 2. As shown in FIG. 2, the heat storage tank 100 hasa tank body 110, and the tank body 110 is constructed by a doublestructure composed of an inner tank portion 111 made of a materialhaving a sufficient corrosion resistance such as a stainless metal, andan outside tank 112. A space between both the tank portions 111, 112 issubstantially evacuated to form a heat insulating layer.

[0029] A first pipe member 113 is inserted into a lower side position ofthe tank body 110 to be welded to both the tank portions 111, 112 of thetank body 110, so that an interior of the tank body 110 communicateswith an exterior of the tank body 110 through the first pipe member 113.A second pipe member 114 made of a material having a sufficientheat-insulating performance, such as a nylon resin, is disposed in thefirst pipe member 113 concentrically with the first pipe member 113. Thesecond pipe member 114 is inserted into both the tank portions 111, 112of the tank body 110 to extend vertically. A flow passage 115 (firstflow passage) through which cooling water in the second cooling watercircuit S2 flows into the tank body 110 is defined between the firstpipe member 113 and the second pipe member 114, and the second pipemember 114 defines therein a flow passage (second flow passage) throughwhich cooling water stored in the tank body 110 flows out. Therefore,cooling water flowing from the engine 200 flows into the tank body 110of the heat storage tank 100 after passing through the flow passage 115from below upwardly.

[0030] An introduction port 116 is opened in the second pipe member 114within the tank body 110 at a position upper than the flow passage 115and lower than a liquid surface of cooling water stored within the tankbody 110. Therefore, cooling water introduced into the second pipemember 114 from the introduction port 116 flows through the second pipemember 114 from an upper side downwardly, and then flows to an outsideof the tank body 110 of the heat storage tank 100.

[0031] A circular plate member 117 for restricting a mixing of coolingwater in the tank body 110 is disposed within the tank body 110 at alower side lower than the introduction port 116, so that cooling waterflowing vertically upwardly from the flow passage 115 collides with theplate member 117. As shown in FIG. 3, the plate member 117 has pluralthrough holes 117 a penetrating through the plate member 117 in athickness direction. The through holes 117 a are provided in such amanner that radial dimensions of the through holes 117 a are increasedas the through holes 117 are positioned to a radial outside.

[0032] In FIG. 2, a housing 118 is disposed at a lower side of the tankbody 110. The housing 118 defines a flow passage 118 a communicatingwith the flow passage 115, and a flow passage 118 b communicating withthe flow passage of the second pipe member 114. Connection pipes 118 c,118 d for connecting a pipe of the second cooling water circuit S2 andthe flow passages 118 a, 118 b are formed in the housing 118. The tankbody 110 is assembled to the vehicle through the housing 118.

[0033] The housing 118 is made of a material similar to that of thesecond pipe member 114. while the housing 118 is fixed to the tank body110, the second pipe member 114 is inserted into the plate member 117and into the housing 118 to be fixed.

[0034] A ring-plate like first valve body 119 for opening and closingthe flow passage 118 a is disposed. The first valve body 19 isconstructed to open the flow passage 118 a when dynamical pressure morethan a predetermined pressure, due to cooling water, is applied to thefirst valve body 119 from below, and to close the flow passage 118 awhen the dynamical pressure lower than the predetermined pressure isapplied to the first valve body 119 from below. Specifically, an openingdiameter d1 of a first valve port 119 a opened and closed by the firstvalve body 119 is made smaller than an outer diameter of the first valvebody 119, and the first valve body 119 is disposed at an upper side ofthe first valve port 119 a. In addition, a density of the first valvebody 119 is made larger than that of cooling water. For example, aspecific gravity of the first valve 119 is approximately 1.64.

[0035] Accordingly, when cooling water flows by the operation of thesecond pump 240, dynamical pressure is applied to the lower side of thefirst valve body 119. Therefore, as shown in FIG. 4, the first valvebody 119 moves upwardly, and the first valve port 119 a (i.e., the flowpassage 115) is opened. Conversely, when the operation of the secondpump 240 is stopped, the dynamical pressure due to cooling water is notapplied to the lower side of the first valve body 119. In this case, asshown in FIG. 2, the first valve body 119 moves downwardly, and closesthe first valve port 119 a. When the first valve port 119 a is closed bythe first valve body 119, the first valve port 119 a (flow passage 118a) is closed by the weight of the first valve body 119 and weight ofcooling water above the first valve body 119. Therefore, the flowpassage 118 a (first valve port 119 a) can be accurately closed by thefirst valve body 119.

[0036] Further, in the first embodiment, a sphere-shaped second valvebody 120 for opening and closing the flow passage 118 b (second valveport 120 a) is disposed. The second valve body 120 is constructed toopen the flow passage 118 b when dynamical pressure larger than apredetermined pressure, due to cooling water, is applied to the secondvalve body 120 from an upper side of the second valve body 120, and toclose the flow passage 118 b when the dynamical pressure lower than thepredetermined dynamical pressure is applied to the second valve body 120from the upper side of the second valve body 120. Specifically, anopening diameter d2 of a second valve port 120 a opened and closed bythe second valve body 120 is made smaller than an outer diameter D2 ofthe second valve body 120, and the second valve body 120 is disposed ata lower side of the second valve port 120 a. In addition, a density ofthe second valve body 120 is made smaller than that of the coolingwater. For example, a specific gravity of the second valve 120 isapproximately 0.98.

[0037] Accordingly, when cooling water flows by the operation of thesecond pump 240, dynamical pressure is applied to the upper side of thesecond valve body 120. Therefore, as shown in FIG. 4, the second valvebody 120 moves downwardly, and the second valve port 120 a (i.e., theflow passage 118 b) is opened. Conversely, when the operation of thesecond pump 240 is stopped, the dynamical pressure is not applied to theupper side of the second valve body 120. In this case, as shown in FIG.2, the second valve body 120 moves upwardly due to the buoyancy, andcloses the second valve port 120 a. A valve-closing force for closingthe second valve port 120 a (flow passage 118 b) is a force due to adensity difference between the second valve body 120 and the coolingwater. However, the valve-closing force is sufficient for preventing aflow of cooling water between an interior of the heat storage tank 100and an exterior of the heat storage tank 100, due to a temperaturedifference between the interior and the exterior of the heat storagetank 100.

[0038] In the first embodiment of the present invention, the flowpassage 118 b is bent to have a vertical passage portion 118 e extendingapproximately vertically, and a horizontal passage portion 118 fextending approximately horizontally.

[0039] Further, the second valve body 120 and the second valve port 120a are provided in a connection portion where the vertical passageportion 118 e and the horizontal passage portion 118 f are connected.Accordingly, when the second valve body 120 moves to the lower side dueto the dynamical pressure, the horizontal passage 118 f may be throttledby the second valve body 120. However, in the first embodiment of thepresent invention, a recessed receiving portion 118 g is provided in thehousing 118 at a position lower than the connection portion between thevertical passage portion 118 e and the horizontal passage portion 118 f.Therefore, when the dynamical pressure is applied to the upper side ofthe second valve body 120 from the upper side, the second valve body 120is received in the receiving portion 118 g, and it can prevent thehorizontal passage portion 118 f from being restricted.

[0040] In addition, a comb-like guide member 121 is disposed to preventthe second valve body 120 from flowing toward the connection pipe 118 d.In the first embodiment of the present invention, both the valve bodies119, 120 are made of a ternary copolymerization rubber of ethylene,propylene and diene (EPDM). However, by changing the polymerizationdegree of the EPDM, the density of the first valve body 119 can bereadily made different from that of the second valve body 120.

[0041] Next, operation of the cooling water circuit according to thefirst embodiment of the present invention will be now described.

[0042] (1) Heat Storage Mode

[0043] The heat storage mode is performed, when the engine 200 operatesand when the temperature T1 (i.e., temperature detected by the firsttemperature sensor 251) of cooling water flowing from the engine 200 isequal to or higher than a predetermined temperature To. Specifically, inthe heat storage mode, high-temperature cooling water flowing from theengine 200 is supplied to the heat storage tank 100 by the operation ofthe second pump 240, and is stored in the tank body 110 of the heatstorage tank 100. The predetermined temperature To is set at atemperature at which a heating operation of the engine 200 can beconsidered to be finished in an engine-heating mode. For example, in thefirst embodiment of the present invention, the predetermined temperatureis −80° C.

[0044] (2) Engine-heating Mode

[0045] The engine-heating mode is performed when the operation of theengine 200 starts. That is, in the engine-heating mode, at the same timeas the start of the engine 200, the second pump 240 is operated.Therefore, in the engine-heating mode, high-temperature cooling waterstored in the heat storage tank 100 is supplied to the engine 200, andthe heating operation of the engine 200 is facilitated.

[0046] In addition, even in a heating operation for heating thepassenger compartment using the heater core 230 in the winter,high-temperature cooling water stored in the heat storage tank 100 canbe supplied to the heater core 230 from a time immediately after thestart of the operation of the engine 200. Therefore, in the heatingoperation, the passenger compartment can be readily quickly heated.

[0047] (3) Cooling Water Holding Mode (First Holding Mode)

[0048] The cooling water holding mode is performed when the temperatureT2 (i.e., the temperature detected by the second temperature sensor 252)of cooling water flowing from the heat storage tank 100 is lower thanthe predetermined temperature To when the engine 200 operates. In thecooling water holing mode, the operation of the second pump 240 isstopped. The cooling water holding mode is changed from theengine-heating mode when all the high-temperature cooling water storedin the heat storage tank 100 flows out in the engine-heating mode.Therefore, it can prevent low-temperature cooling water flowing from theengine 200 from being stored in the heat storage tank 100 and fromflowing into the engine 200. Accordingly, the heating operation of theengine 200 can be further facilitated.

[0049] When a capacity of the tank body 110 is set more than an amountof cooling water in the engine 200, the heating operation of the engine200 can be further effectively facilitated. When the temperature T1 ofcooling water flowing from the engine 200 is higher than thepredetermined temperature To, the heat storage mode is set from thecooling water holding mode.

[0050] 4. Hot Water Holding Mode (Second Holding Mode)

[0051] The hot water holding mode is performed when the operation of theengine 200 stops. In the hot water holding mode, the operation of thesecond pump 240 stops, and high-temperature cooling water (hot water)stored in the heat storage tank 100 during the heat storage mode isstored by heat insulation.

[0052] According to the first embodiment of the present invention, thefirst and second valve ports 119 a and 120 a (flow passages 118 a and118 b) are opened and closed by the dynamical pressure applied to thefirst and second valve bodies 119, 120, respectively. Therefore, thestructure of a valve portion for controlling a flow of cooling water inthe heat storage tank 100 can be made simple, and component number forthe valve member can be relatively made smaller. Thus, the heat storagetank 100 can be manufactured in low cost.

[0053] In the first embodiment of the present invention, the secondcooling water circuit S2 provided with the heat storage tank 100 isprovided separately independently with the first cooling water circuitS1 having the heater core 230 and the radiator 210. Therefore,high-temperature cooling water can be directly supplied to the engine200 from the heat storage tank 100 at a requisite time without beingaffected by the operation of the heater core 230 or the radiator 210.Thus, the heating operation of the engine 200 can be effectivelyfacilitated.

[0054] The tank body 110 has the double tank structure with a sufficientheat-insulating performance. However, in an opening portion of the tankbody 110, where the first pipe member 113 and the second pipe member 114are inserted, the interior of the tank body 110 is thermally connectedto an exterior of the tank body 110. Therefore, heat of hot water(cooling water) in the tank body 110 is readily radiated from theopening portion of the tank body 110. On the other hand, the temperatureof hot water in the tank body 110 is lowered as a lower position in thetank body 110. Thus, in the first embodiment, the opening portion of thetank body 110 is provided at a lower side position of the tank body 110so that a temperature difference between the interior and the exteriorof the tank body 110 is made smaller in the opening portion of the tankbody 110. Accordingly, in the first embodiment, a heat radiation fromthe opening portion of the tank body 110 can be restricted, andheat-insulating performance of the tank body 110 can be improved.

[0055] A second preferred embodiment of the present invention will benow described with reference to FIGS. 5 and 6. In the above-describedfirst embodiment of the present invention, when the second pump 240operates, the second valve body 120 is pressed by the dynamical pressureapplied to the second valve body 120 to be moved downwardly. However, bya balance between the dynamical pressure applied to the second valvebody 120 and the buoyancy applied to the second valve body 120, thesecond valve body 120 may be not moved to the receiving portion 118 g,but may be moved to a position (guide member 121) corresponding to thehorizontal passage portion 118 f as shown in FIG. 5. When the secondvalve body 120 is positioned at the position corresponding to thehorizontal passage portion 118 f as shown in FIG. 5, the flow of coolingwater in the horizontal passage portion 118 f is restricted by thesecond valve body 120, and a flow resistance of cooling water isincreased.

[0056] Accordingly, in the second embodiment of the present invention,as shown in FIG. 6, a receiving portion 118 g for receiving the secondvalve body 120 is provided at a side opposite to the horizontal passageportion 118 f. That is, at both opposite sides of the connection portionbetween the vertical passage portion 118 e and the horizontal passageportion 118 f, the horizontal passage portion 118 f and the receivingportion 118 g are provided opposite to each other. In addition, a guideportion 118 j having a taper surface 118 h is provided in the connectionportion so that the second valve body 120 moves into the receivingportion 118 g by the guiding of the taper surface 118 h.

[0057] Thus, in the second embodiment, it can prevent the flow ofcooling water from being restricted by the second valve body 120 whenthe dynamical pressure is applied to second valve body 120, and it canprevent the flow resistance of cooling water from being increased.

[0058] A third preferred embodiment of the present invention will be nowdescribed with reference to FIGS. 7 and 8. As shown in FIGS. 7 and 8, inthe third embodiment of the present invention, the second valve body 120is disposed inside the second pipe member 114 to be positioned withinthe tank body 110. Accordingly, in the third embodiment, the receivingportion 118 g described in the first and second embodiments isunnecessary, and a size of the housing 118 can be reduced.

[0059] In the third embodiment, the second pipe member 114 is providedin such a manner that, a hole diameter d2 of a pipe part from the secondvalve port 120 a toward the introduction port 116 is made smaller thanthe diameter D2 of the second valve body 120, and a hole diameter d3 ofa pipe part from the second valve port 120 a toward the housing 110(downside) is made larger than the diameter D2 of the second valve body120. The second pipe member 114 is provided with a male screw portion(not shown) at a lower side end, and the male screw portion of thesecond pipe member 114 is screwed into a female screw portion providedin the housing 118 so that the second pipe member 114 is fixed to thehousing 118.

[0060] Accordingly, in the third embodiment of the present invention,when the dynamical pressure is applied to the second valve body 120 bythe operation of the second pump 240, cooling water flowing from thesecond valve port 120 a downwardly flows toward the connection pipe 118d after flowing around the second valve body 120 as shown in FIG. 8. Inthe third embodiment, FIG. 7 shows a state where the valve ports 119 a,120 a are closed by the first and second valve bodies 119, 120,respectively, when the operation of the second pump 240 stops.

[0061] A fourth preferred embodiment of the present invention will benow described with reference to FIG. 9. In the fourth embodiment of thepresent invention, a collision member 122, to which cooling waterflowing from a flow port 115 a of the flow passage 115 collides, isprovided at a position near the flow port 115 a of the flow passage 115.The collision member 122 and the plate member 117 described in the firstembodiment can be integrally formed by a stainless metal, for example.

[0062] The collision member 122 includes a cover member 122 a disposedopposite to the flow port 115 a to have a predetermined space betweenthe flow port 115 a and the cover member 122 a, and a guide portion 122b connected to the cover member 122 a to extend downwardly. That is, asshown in FIG. 9, the guide portion 122 b connected to the cover member122 a is disposed to cover the flow port 115 a around an entire outerperiphery of the flow port 115 a at a position away from the flow port115 a by a predetermined dimension. Further, in the fourth embodiment,the plate member 117 is provided around the flow port 115 a to extendfrom an end portion of the guide portion 122 b to an inner wall of thetank body 110. The cover member 122 a of the collision member 122 isused as a stopper member for preventing the first valve body 119 frombeing away from the flow port 115 a more than a predetermined dimension.

[0063] For improving the heat insulating performance of the heat storagetank 100, the opening portion of the tank body 110 is made smaller aspossible. However, in a case where the opening area of the openingportion of the tank body 110 is made smaller, when the flow amount ofcooling water flowing into the tank body 110 is made larger, a flow rateof cooling water flowing into the tank body 110 from the opening portionis increased, and cooling water passes through the holes 117 a of theplate member 117 when only the plate member 117 described in the firstembodiment is disposed in the heat storage tank 100. In this case,cooling water in the tank body 110 is mixed, and cooling water mayforcedly circulate in the tank body 110.

[0064] However, in the fourth embodiment of the present invention, thecollision member 122 having an approximate cup shape is provided aroundthe flow port 115 a. Therefore, even when a water flow with a high flowrate is injected toward an upper side from the flow port 115 a, thewater flow collides with the cover member 122 a and are turned by anapproximate right angle 90°, and thereafter are turned downwardly.Accordingly, after the flow rate of cooling water from the flow port 115a is sufficiently reduced by the collision member 122, the water flow isintroduced to a lower side of the plate member 117.

[0065] According to the fourth embodiment of the present invention, theupwardly injected flow of cooling water can be accurately changed sothat cooling water from the flow port 115 a is introduced at the lowerside of the plate member 117. Therefore, even when cooling water havinga large flow rate is injected from the flow port 115 a, it can preventcooling water in the tank body 110 from being mixed, whileheat-insulating performance of the heat storage tank 100 can beimproved.

[0066] Further, because the guide portion 122 b is provided along allthe outer periphery of the flow port 115 a, the mixing of cooling waterin the tank body 110 can be further effectively prevented.

[0067] A fifth preferred embodiment of the present invention will be nowdescribed with reference to FIGS. 10A and 10B. As shown in FIGS. 10A and10B, a valve seat 114 a, 114 b is provided to define the valve port 120a, so that a surface of the second valve body 120 contacts the valveseat 114 a, 114 b. For example, when the second valve body 120 has asphere shape as shown in FIG. 10A, the valve seat 114 a is formed tohave a spherical surface. On the other hand, when the valve body 120 hasa conical shape as shown in FIG. 10B, the valve seat 114 b is formed tohave a conical taper shape.

[0068] When the second pipe member 114 (flow passage) is closed by thesecond valve body 120, heat in the tank body 110 of the heat storagetank 100 is radiated to an outside of the heat storage tank 100 througha position (valve port 120 a) in the second pipe member 114, on whichthe second valve body 120 contacts. In the fifth embodiment of thepresent invention, the valve seat 114 a, 114 b contacting the secondvalve body 120 in the second valve port 120 a is provided. That is, byproviding the valve seat 114 a, 114 b, a contacting area of the secondvalve body 120 contacting the second pipe member 114 can be increased,and a heat-transmitting path for transmitting heat from the interior ofthe heat storage tank 100 to the exterior of the heat storage tank 100can be elongated. Therefore, heat-insulating capacity of the heatstorage tank 100 can be improved.

[0069] In the fifth embodiment of the present invention, the shape ofthe valve seat 114 a, 114 b is not limited to the shapes shown in FIGS.10A and 10B, but can be suitably changed in accordance with the shape ofthe valve body 120.

[0070] Although the present invention has been fully described inconnection with the preferred embodiments thereof with reference to theaccompanying drawings, it is to be noted that various changes andmodifications will become apparent to those skilled in the art.

[0071] For example, in the above-described first embodiment of thepresent invention, the first valve body 119 and the second valve body120 are made of a rubber (e.g., EPDM). However, the valve bodies 119,120 can be made of the other material such as a metal, a resin, a foammember, a hollow member and a sponge member. Further, the shapes of thefirst and second valve bodies 119, 120 can be changed to the othershapes such as a conical shape, a cylindrical shape and a fusiformshape.

[0072] In the above-described embodiments of the present invention, theopening portion of the tank body 110 is provided at a lower sideposition of the tank body 110 so that the housing 118 and the first pipemember 113 are positioned at the lower side of the tank body 110.However, the housing 118 and the opening of the tank body 110 may bepositioned at an upper side of the tank body 110 or may be positioned atthe other side.

[0073] In the above-described embodiments of the present invention, theflow passage is closed when the dynamical pressure is smaller than thepredetermined pressure by using the density difference between thecooling water and the first and second valve bodies 119, 120. However,an elastic member such as a spring can be disposed so that a forceopposite to the dynamical pressure is applied to the first or secondvalve body 119, 120. In this case, the flow passage is opened and closedby the valve body 119 or 120 by a balance between the force due to thedynamical pressure and a force due to the elastic member. Alternatively,an elastic member can be provided, so that the flow passage is openedand closed by a balance of the force due to the elastic member, theforce of the dynamical pressure and the density difference between thecooling water and the valve body 119, 120.

[0074] In the above-described embodiment of the present invention, boththe valve bodies 119, 120 are provided in both the flow passages in theheat storage tank 100 at inlet position and an outlet position. However,one valve body can be provided for one flow passage in the heat storagetank 100.

[0075] Such changes and modifications are to be understood as beingwithin the scope of the present invention as defined by the appendedclaims.

What is claimed is:
 1. A heat storage tank for storing a cooling liquidof a liquid-cooled engine in a cooling liquid circuit by heatinsulation, the heat storage tank comprising: a tank body in which thecooling liquid is stored by heat insulation; a connection memberconnected to the tank body, for defining a fluid passage communicatingwith an interior of the tank body, through which cooling liquid in thecooling liquid circuit flows; a valve body for opening and closing thefluid passage, wherein the valve body is constructed to open the fluidpassage when a dynamical pressure due to the cooling liquid, larger thana predetermined pressure, is applied to the valve body, and to close thefluid passage when the dynamical pressure smaller than the predeterminedpressure is applied to the valve body.
 2. The heat storage tankaccording to claim 1, wherein the valve body is constructed to close thefluid passage by a density difference between the cooling liquid and thevalve body when the dynamical pressure applied to the valve body issmaller than the predetermined pressure.
 3. The heat storage tankaccording to claim 1, wherein the valve body is constructed to close thefluid passage by a pressure due to a weight of the valve body and aweight of the cooling liquid when the dynamical pressure applied to thevalve body is smaller than the predetermined pressure.
 4. The heatstorage tank according to claim 1, wherein the connection member isdisposed to be connected to a lower side position of the tank body insuch a manner that the fluid passage communicates with the interior ofthe tank body at a lower side in the tank body.
 5. The heat storage tankaccording to claim 1, wherein: the connection member is disposed so thatcooling liquid in the cooling liquid circuit flows into the tank bodyfrom below upwardly through the fluid passage; the valve body has adensity larger than that of the cooling liquid to have a densitydifference between the valve body and the cooling liquid; and the valvebody is disposed to open the fluid passage when the dynamical pressurelarger than the predetermined pressure is applied to a lower side of thevalve body, and to close the fluid passage by the density differencewhen the dynamical pressure applied to the lower side of the valve bodyis smaller than the predetermined pressure.
 6. The heat storage tankaccording to claim 1, wherein: the connection member is disposed so thatcooling liquid in the tank body flows out from an upper side downwardlythrough the fluid passage; the valve body has a density smaller thanthat of the cooling liquid to have a density difference between thecooling liquid and the valve body; and the valve body is disposed toopen the fluid passage when the dynamical pressure larger than thepredetermined pressure is applied to an upper side of the valve body,and to close the fluid passage by the density difference when thedynamical pressure applied to the upper side of the valve body issmaller than the predetermined pressure.
 7. The heat storage tankaccording to claim 1, further comprising a collision member disposed inthe tank body so that cooling liquid flowing into the tank body from afluid port of the fluid passage collides with the collision member,wherein, the collision member has a cover member disposed opposite tothe flow port at a position away from the flow port by a predetermineddistance, and a guide member extending from the cover member to aperipheral side of the fluid port.
 8. The heat storage tank according toclaim 7, wherein the guide member is disposed at a position away fromthe flow port by a predetermined distance to cover the flow port alongan entire outer periphery of the fluid port.
 9. The heat storage tankaccording to claim 7, further comprising a plate member having aplurality of holes, for restricting a mixing of cooling liquid in thetank body when the cooling liquid flows into the tank body from thefluid port, wherein the plate member is disposed between the collisionmember and an inner wall of the tank body around the fluid port.
 10. Theheat storage tank according to claim 9, wherein the collision member andthe plate member are formed integrally.
 11. The heat storage tankaccording to claim 1, wherein the fluid passage has a valve port definedby a wall portion which contacts the valve body when the fluid passageis closed by the valve body.
 12. The heat storage tank according toclaim 11, wherein the wall portion defining the valve port has a valveseat on which a surface of the valve body contacts when the fluidpassage is closed by the valve body.
 13. A heat storage tank for storinga cooling liquid of a liquid-cooled engine in a cooling liquid circuitby heat insulation, the heat storage tank comprising: a tank body inwhich the cooling liquid is stored by heat insulation; a connectionmember connected to the tank body, for defining a first fluid passagethrough which cooling liquid in the cooling liquid circuit flows intothe tank body upwardly from a lower side, and a second fluid passagethrough which cooling liquid flows out from the tank body downwardlyfrom an upper side; a first valve body for opening and closing the firstfluid passage; and a second valve body for opening and closing thesecond fluid passage, wherein: the first valve body has a density largerthan that of the cooling liquid, and the second valve body has a densitysmaller than that of the cooling liquid; the first valve body isdisposed to open the first fluid passage when a dynamical pressure dueto the cooling liquid, larger than a predetermined pressure, is appliedto the first valve body from a lower side, and to close the first fluidpassage when the dynamical pressure applied to the first valve body issmaller than the predetermined pressure; and the second valve body isdisposed to open the second fluid passage when the dynamical pressurelarger than the predetermined pressure is applied to the second valvebody from an upper side, and to close the second fluid passage when thedynamical pressure applied to the second valve body is smaller than thepredetermined pressure.
 14. The heat storage tank according to claim 13,wherein the first fluid passage and the second fluid passage areprovided at a lower side of the tank body to communicate inside the tankbody.
 15. The heat storage tank according to claim 13, furthercomprising a collision member disposed in the tank body so that coolingliquid flowing into the tank body from a fluid port of the first fluidpassage collides with the collision member, wherein, the collisionmember has a cover member disposed opposite to the flow port at aposition away from the flow port by a predetermined distance, and aguide member extending from the cover member to a peripheral side of thefluid port.
 16. The heat storage tank according to claim 15, wherein theguide member is disposed at a position away from the flow port by apredetermined distance to cover the flow port along an entire outerperiphery of the fluid port.
 17. The heat storage tank according toclaim 15, further comprising a plate member having a plurality of holes,for restricting a mixing of cooling liquid in the tank body when thecooling liquid flows into the fluid tank from the fluid port, whereinthe plate member is disposed between the collision member and an innerwall of the tank body around the fluid port.
 18. The heat storage tankaccording to claim 17, wherein the collision member and the plate memberare formed integrally.
 19. The heat storage tank according to claim 13,wherein: the first fluid passage has a first valve port defined by afirst wall portion which contacts a surface of the first valve body whenthe first fluid passage is closed by the first valve body; and the firstfluid passage has a second valve port defined by a second wall portionwhich contacts a surface of the second valve body when the second fluidpassage is closed by the second valve body.
 20. A cooling liquid circuitfor liquid-cooled engine, in which a cooling liquid circulates, thecooling liquid circuit comprising: a first liquid circuit including atleast a radiator for cooling the cooling liquid; a second liquid circuitincluding a heat storage tank for storing the cooling liquid by heatinsulation; and a pump disposed in the second liquid circuit in such amanner the cooling liquid circulates between the second cooling liquidcircuit and the liquid-cooled engine independently with the first liquidcircuit, wherein: the heat storage tank includes a tank body in whichthe cooling liquid is stored by heat insulation, a fluid passage throughwhich cooling liquid in the second liquid circuit communicates with aninterior of the tank body, and a valve body for opening and closing thefluid passage; and the valve body is constructed to open the fluidpassage when a dynamical pressure due to the cooling liquid in thesecond liquid circuit, larger than a predetermined pressure, is appliedto the valve body, and to close the fluid passage when the dynamicalpressure applied to the valve body is smaller than the predeterminedpressure.